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Circuit Design for Moisture Sensor Amplifier

Question

Design a circuit that amplifies signals from a moisture sensor whose terminal resistance varies over a range from 0.1mΩ to 10Ω when biased at a current level of 1mA. Assume the signal varies over a frequency range of 100 to 20,000 Hz.  The amplified signal is to be connected to the ADC port of a microcontroller that accepts signals in the range from 0 to 3.3V as shown in Fig.1. The input resistance and capacitance seen looking into the ADC input port is approximately 1MΩ and 10pF.
Also, your job is to design the DC power supply for the transducer and CMOS amplifier as shown in Fig. 2. The microcontroller is connected to a separate power supply of 3.3 V; it is important that these two systems share the same ground. The amplifier can be constructed using op amps or CMOS transistors or a combination of both. The op amps should be of the 741-type powered from a bipolar power supply (±VDD).  If you chose to go the op amp route, you must design a bipolar power supply.

For the whole question please refer to the PDF document attached.

Summary

The question belongs to Electronics and the question is about preparing or designing a circuit which amplifies signals from a moisture sensor. The solution contains the circuit design schema and the output details of the circuit.

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    tina Johnson

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    Giuseppe

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